Method for manufacturing a semiconductor device

Abstract

A method for manufacturing steps of depositing phosphorus onto separate portions of a silicon substrate, covering only one portion with a polycrystalline silicon layer and heating the deposited phosphorus on the separate portions at the same time to diffuse thereby forming two diffusion layers of different depths.

What we claim is: 
     
       1. A method for manufacturing a semiconductor device comprising a first step for preparing a silicon body, a second step for forming first and second n-type regions by depositing phosphorus separately on two portions on said body, a third step for forming a polycrystalline silicon layer on said first n-type region, and a fourth step for heating to diffuse phosphorus within said first and second n-type regions, to form a shallow first diffused region and a deep second diffused region separately in said body. 
     
     
       2. A method according to claim 1, wherein said third step is a process for forming a polycrystalline silicon layer doped with an n-type impurity with a diffusion coefficient smaller than that of phosphorus. 
     
     
       3. A method according to claim 1 or 2, wherein said first step includes preparing an n-type silicon substrate and forming first and second p-type base regions on one side of said substrate, said two base regions being separated from each other, and said second step includes depositing phosphorus separately on portions on said first and second base regions. 
     
     
       4. A method according to claim 3, wherein said second step is a process for depositing phosphorus by decomposing phosphorus oxychloride. 
     
     
       5. A method according to claim 3, wherein said second step is a process for depositing phosphorus ions by ion implantation.